Direct positive recording film



United States Patent 3,510,348 DIRECT POSITIVE RECORDING FILM Dugald A.Brooks, Evan T. Jones, and Richard W. Spayd, Rochester, N .Y., assignorsto Eastman Kodak Company, Rochester, N.Y., a corporation of New JerseyNo Drawing. Filed June 20, 1966, Ser. No. 558,585 Int. Cl. B4411 N18 US.Cl. 117-201 31 Claims ABSTRACT OF THE DISCLOSURE This invention relatesto electron-sensitive recording elements and processes of exposing toelectrons an electrically conductive element comprising a support and alayer comprising electron-sensitive, direct-positive, fogged silverhalide grains.

This invention relates to electron sensitive recording elements, theirpreparation and use. In one of its aspects this invention relates toelectrically conducting electron sensitive elements comprising a supportin which silver halide layers for-m direct-positive images upondevelopment following exposure to e ectrons. In another of its aspects,this invention relates to electron sensitive films and plates which canbe exposed to electrons in a vacuum to obtain direct-positive silverimages.

Electron sensitive films and plates are useful in many applications forrecording an image by direct exposure to an electron beam, for examplein a cathode ray tube, in electron microscopes, data recording apparatusand the like. Such films and plates comprise a layer of electronsensitive material that forms an image in the layer by direct imagewiseexposure in an electron beam The image produced can be directly visibleas in a layer of monomeric material that polymerizes upon electron beamexposure or it can be a latent image that requires development toproduce a visible image as with silver halide materials.

In some recording apparatus that employ direct electron beam recordingfilm, an image recorded on the film or plate is read back or viewed byprojecting a beam of ultraviolet or other radiation through thedeveloped film onto a fluorescent screen to produce a fluorescent imageon the screen. However, for many uses it is desirable to view the imagedirectly on the film by irradiating a fluorescent layer which is coatedon the film or plate after exposure and prior to read-out. See, forexample, B. Miller, Electron Beam Read-Out Shows Potentia Aviation Weekand Space Technology, Apr. 13, 1964, pages 107-110, and a paperpresented at the National Aerospace Electronics Conference, 17th.Dayton, Ohio, 1965, by E. V. Boblett and K. F. Wallace, entitledElectron Beam Readout of Silver Halide Transparencies. The fluorescentlayers employed in electron beam recording films or plates can beincorporated into such materials during their manufacture in order tofacilitate handling prior to read-out.

In the past, the electron sensitive materials employed in electronrecording films and plates have been negative silver halide layers,i.e., those which upon simple or single stage development give negativesilver images. In many cases, however, it is desirable or even necessaryto obtain positive silver images. Unfortunately, the negative silverhalide layers used for this purpose require complex multi. stagereversal processing in order to obtain a positive image. Furthermore,silver halides having fine grains are especially useful in electronsensitive films and plates due to their high resolution and lowgraininess characteristics. However, when employing conventionalmultistage reversal processing techniques with fine grain silver halide3,510,348 Patented May 5, 1970 ice layers it is extremely diflicult toobtain the sensitometric characteristics required in electron recording.

Accordingly, it is an object of this invention to provide electronsensitive elements which contain a layer of silver halide grains. It isanother object of this invention to provide an electrically conductiveelement comprising a support and a layer of electron sensitivedirect-positive fogged silver halide grains. Still another object ofthis invention is to provide an electron sensitive element which can beprocessed by simple one-stage development to obtain a positive silverimage. Still another object of this invention is to provide an electronsensitive element that can be exposed to electrons in a vacuum to obtaina positive silver image upon simple one-stage development. It is anotherobject of this invention to provide a simple, rapid and economical meansfor obtaining a positive silver image with an electron sensitivephotographic element. Other objects and advantages of this inventionwill become apparent from an examination of the specification and claimswhich follow.

The above and other objects of this invention are obtained with directeectron recording films and plates having radiation sensitive layerswhich comprise fogged silver halide grains which form a direct-positivesilver image upon simple or single stage development following exposureto electrons. Since these fogged silver halide grains form positivesilver images after exposure to electrons without complex multistagereversal processing they are referred to in the following specificationand claims as electron sensitive direct-positive fogged silver halidegrains.

To obtain fogged silver ha ide grains which will form direct-positivesilver images upon exposure to electrons it is sometimes desirable oreven necessary to include an electron acceptor, more specifically aphotoelectron acceptor or a desensitizing dye in the layer with thefogged silver halide grains. Such electron accepting compounds areabsorbed to the silver halide grains and often improve the electronsensitivity of such grains. In the past, electron acceptors have beenused in light sensitive direct-positive silver halide layers to improvethe reversal characteristics of the layer upon exposure to light. However, a surprising feature of this invention is that many lightsensitive direct-positive silver halide layers containing electronacceptors are not electron sensitive and cannot be used in the practiceof this invention, as shown in Example 3. Furthermore, certain of thefogged silver halide grains disclosed herein, as illustrated in thefollowing Example 1, exhibit very useful reversal characteristics in theabsence of an electron accepting compound.

The silver halide grains employed in the practice of this invention arelight sensitive, i.e., they are photographic silver halides, as well asbeing sensitive to electrons and can be prepared using methods known inthe photographic art. A preferred class of silver halide grainscomprises a central core of a silver halide containing centers whichpromote the deposition of photolytic silver and an outer shell orcovering for such core of a fogged or spontaneously developable silverhalide. Silver halide grains containing such fogged shells develop tosilver without exposure.

Before shell formation, the core forming photographic silver halide ischemically or physically treated by methods previously described in theprior art to produce centers to promote the deposition of photolyticsilver, i.e., latent image nucleating centers. Such centers can beobtained by various techniques as described herein. Chemicalsensitization techniques of the type described by Antoine Hautot andHenri Saubenier in Science et Industries Photographiques, Vol. XXVIII,January 1957, pages 57 to 65, are particularly useful. Such chemicalsensitization includes three major classes, namely, gold or noble metalsensitization, sulfur sensitization, such as by a labile sulfurcompound, and reduction sensitization, i.e., treatment of the silverhalide with a strong reducing agent which introduces small specks ofmetallic silver into the silver salt crystal or grain.

When the core forming emulsion is chemically sensitized, it ispreferably sensitized so that when examined according to normalphotographic testing techniques by coating a test portion of theemulsion on a transparent support, exposing to a light intensity scalefor a fixed time between 0.01 and 1 second and development for 6 minutesat 68 F. in Developer A, as hereinafter defined, it has a sensitivitygreater than the sensitivity of an identical test portion of the sameemulsion (measured at a density of 0.1 above fog), which has beenexposed in the same way, bleached minutes in an aqueous 0.3 percentpotassium ferricyanide solution at 65 F., and developed for 5 minutes at65 F., in Developer B, as hereinafter defined. Developer A is the usualtype of surface image developer and Developer B is an internal developerhaving high silver halide solvent activity.

DEVELOPER A Grams N-methyl-p-aminophenol sulfate 2.5 Ascorbic acid 10.0Potassium meta'borate 35.0 Potassium bromide 1.0 Water to make 1 liter.pH of 9.6.

DEVELOPER B Grams N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite,desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5Potassium bromide 5.0 Sodium thiosulfate 10.0

Water to make 1 liter.

The core forming emulsions can be chemically sensitized by any methodsuitable for this purpose. For example, the core forming emulsions canbe digested with naturally active gelatin, or sulfur compounds can beadded, such as those described in Sheppard U.S. Pat. 1,574,944, issuedMar. 2, 1926; Sheppard et a1. U.S. Pat. 1,623,499, issued Apr. 5, 1927;and Sheppard et al. U.S. Pat. 2,410,689, issued Nov. 5, 1946.

The core forming emulsions can also be chemically sensitized with goldsalts as described in Waller et al. U.S. Pat. 2,399,083, issued Apr. 23,1946, and Damschroder et a1. U.S. Pat. 2,642,361, issued June 16, 1953.Suitable compounds are potassium chloroaurite, potassiumaurithiocyanate, potassium chloroaurate, auric trichloride and2-aurosulfobenzothiazole methochloride.

The core forming emulsions can also be chemically sensitized withreducing agents, such as stannous salts (Carroll U.S. Pat. 2,487,850,issued Nov. 15, 1949), polyamines, such as diethylene triamine (Lowe andJones U.S. Pat. 2,518,698, issued Aug. 15, 1950), polyamines, such asspermine (Lowe and Allen U.S. Pat 2,521,925, issued Sept. 12, 1950), orbis(p-aminoethyl)sulfide and its Water-soluble salts (Lowe and JonesU.S. Pat. 2,521,- 926, issued Sept. 12, 1950).

The core forming emulsions can also be treated during or after theformation of the silver halide with salts of polyvalent metals such asbismuth, the noble metals and/ or the metals of Group VIII of thePeriodic Table, such as ruthenium, rhodium, palladium, iridium, osmium,platinum and the like. Representative compounds are ammoniumchloropalladate, potassium chloroplatinate, sodium chloropalladite andthe like.

The core forming emulsions can also be subjected to fogging by exposureto light either to low or high intensity light, to produce centers whichpromote the deposition of photolytic silver prior to forming the shellthereon.

The shell of the aforementioned silver halide grains can be prepared byprecipitating over the core grain a light-sensitive silver halide thatcan be fogged and which fog is removable by bleaching. The shell is ofsufiicient thickness to prevent access of the' developer used inprocessing the silver halides to the core. The silver halide shell issurface fogged to make it developable to metallic silver withconventional surface image developing compositions. Such fogging can beeffected by chemically sensitizing to fog with the sensitizing agentsdescribed for chemically sensitizing the core forming emulsion, highintensity light and like fogging means well known to those skilled inthe art. While the core need not be sensitized to fog, the shell isfogged, for example, reduction fogged With a reducing agent such asstannous chloride. Fogging by means of a reduction sensitizer, a noblemetal salt such as a gold salt plus a reduction sensitizer, high pH andlow pAg silver halide precipitating conditions, and the like can besuitably utilized.

In one embodiment of the invention, the core of the above grains in theelectron sensitive layer is a coarse grained silver halide and a silverhalide from a finer grained silver halide is deposited thereon byOstwald ripening to form the shell. Also, coarse grained silver halidescan be used to form a shell over a finer grained core when theshell-forming silver halide is more watersoluble than the core silverhalide. In another embodiment of the invention the silver halide shellis formed immediately after formation of the core without interruptingthe precipitation, as shown in Example -1. Generally, about 2 to 8 molarequivalents of shell silver halide per molar equivalent of core silverhalide are used in the grains comprising the electron sensitive layersemployed in this invention. These silver halides can be termed coveredgrains and emulsions containing them covered grain emulsions. Thepopulation of grains in such emulsions are substantially uniform ingrain-size distribution, as contrasted with emulsion blends whichcontain at least two types of grains, which are separate and distinct intheir physical, and frequently, photographic properties. The grain sizeof these covered grain emulsions widely varies, typical emulsions havingan average grain size of about 0.05 to 10 microns in diameter. Suchgrains are generally coated at silver coverages in the range of about 10to about 400 mg. silver/fif preferably about 20 to about mg. silver/ft.and when exposed to an image and thereafter developed in a conventionalsurface image developer having low silver salt solvent action, form areversal or direct-positive silver image. The unexposed grains developwithout substantial reduction of the imagewise exposed grains.

Another class of electron sensitive direct-positive fogged silver halidegrains that can be employed in the practice of this invention are thenon covered grain fogged silver halides. Such grains can be fogged bychemically sensitizing into fog with the sensitizing agents describedfor chemically treating the core-forming emulsions describedhereinbefore. Thus, suitable fogging methods include chemicalsensitization techniques of the type described by Antoine Hautot andHenri Saubenier in Science et Industries Photographiques, Vol. XXVIII,January 1957, pages 57 to 65. The silver halide grains can be foggedwith high intensity light, reduction fogged with a reducing agent suchas thiourea dioxide or stannous chloride or fogged with gold or othernoble metal compounds. Combinations of reduction fogging agents withgold compounds or compounds of another metal more electropositive thansilver, for example, rhodium, platinum or iridium, can be used infogging the silver halide grains.

The silver halide grains employed in the practice of this invention arefogged sufliciently to give a density of at least 0.5 when developedwithout exposure for five minutes in Kodak DK-SO developer when adirect-positive emulsion layer containing such grains is coated at acoverage of about 50 to about 500 mg. of silver per square foot ofsupport.

As previously stated, the direct-positive fogged silver halide grainsemployed in the conducting elements of this invention can comprisereduction and gold fogged silver halide grains, which are fogged with acombination of a reduction fogging agent and a gold fogging agent. Whena low concentration of gold and reducing agent is employed in such acombination the fogged silver halide grains are characterized by a rapidloss of fog upon chemical bleaching, as described hereinafter.

In practicing this invention, the silver halide grains can be foggedprior to coating or they can be coated prior to fogging. The reactionconditions during fogging of the silver halide grains are subject towide variation although the pH is generally in the range of about 5 toabout 7, the pAg is generally in the range of about 7 to about 9 and thetemperature is generally in the range of about 40 to about 100 C., mostoften about 50 to about 70 C. During fogging the silver halide grainscan be suspended in a suitable vehicle such as gelatin which isgenerally employed at a concentration in the range of about 40 to about200 grams per mole of silver halide.

As previously indicated, a preferred class of silver halide grains arethose which are characterized by a rapid loss of fog upon chemicalbleaching. These grains will lose at least about 25% and generally atleast about 40% of their fog when bleached for ten minutes at 68 F., ina potassium cyanide bleach composition as described hereinvent solution,for example methanolic solutions of the electron acceptor which are 0.05molar in sodium acetate and 0.005 molar in acetic acid using a carbonpaste of pyrolytic graphite electrode, with the voltometric half peakpotential for the most negative anodic response being designated E,,. Ineach measurement, the reference electrode can be an aqueoussilver-silver chloride (saturated potassium chloride) electrode at 20 C.Electrochemical measurements of this type are known in the art and aredescribed in New Instrumental Methods in Electrochemistry, by Delahay,Interscience Publishers, New York, N.Y., 1954; Polarography, by Kolthoffand Lingane, 2nd Edition, Interscience Publishers, New N. Y., 1952;Analytical Chemistry, 36, 2426 (1964) by Elving; and AnalyticalChemistry, 30, 1576 (1958) by Adams. Compounds which can be employed aselectron acceptors in the practice of this invention include organiccompounds having an anodic polarographic halfway potential (E,,) and acathodic polarographic halfway potential (E which when added togethergive a positive sum of greater than 0.5, preferably greater than 0.97.Some specific electron acceptors which give outstanding results in thepractice of this invention are cyanine dyes having at least one methinegroup wherein the hydrogen atom thereof is replaced with a halogen atomhaving an atomic Weight in the range of about 35 to about 127, i.e.,chlorine, bromine or iodine atoms. Suitable halogen containing cyaninedyes can be repreafter. This fog loss can be illustrated by coating theregusented by the formula:

lar silver halide grains as a photographic silver halide emulsion on asupport to give a maximum density of at least 1.0 When processed for sixminutes at about 68 F., in Kodak DK-SO developer and comparing thedensit of such a coating with an identical coating which is processedfor six minutes at 68 F., in Kodak DK-50 developer after being bleachedfor about 10 minutes at 68 F., in the potassium cyanide bleachcomposition. The maximum density of the unbleached coating will be atleast 30% greater, generally at least 60% greater than the maximumdensity of the bleached coating. Kodak DK-50 developer is described inthe Handbook of Chemistry and Physics, 30th Edition, 1947, ChemicalRubber Publishing Co., Cleveland, Ohio, page 2558, and has the followingcomposition:

Water, about 125 F. (52 C.)500 cc. N-methyl-p-aminophenol sulfate2.5grams Sodium sulfite, desiccated30.0 grams Hydroquinone-2.5 grams Sodiummetaborate10.0 grams Potassium bromide-05 gram Water to make 1.0 liter 7In practicing this invention, it is sometimes desirable or evennecessary to employ an electron accepting compound with the foggedsilver halide grains in order to obtain optimum reversalcharacteristics. Suitable electron accepting compounds include thephotoelectron accepting compounds or desensitizing dyes often used inphotographic reversal systems. These electron accepting compounds areabsorbed to the fogged silver halide grains. The electron acceptorswhich give particularly good results in the practice of this inventioncan be characterized in terms of their polarographic halfwavepotentials, i.e., their oxidation reduction potentials determined bypolarography. Cathodic measurements can be made with 1 10- molarsolution of the electron acceptor in a solvent, for example methanolwhich is 0.05 molar in lithium chloride using a dropping mercuryelectrode with a polarographic halfwave potential for the most positivecathodic wave being designated E Anodic measurements can be made with l10 molar aqueous sol- /p-l\ jut-1 wherein Z and Z each represent thenon-metallic atoms necessary to complete a heterocyclic nucleus of thetype used in cyanine dyes, such as a nucleus of the benzothiazole series(e.g., benzothiazole, 4-chlorobenzothiazole, 5-chlorobenzothiazole,7-chlorobenzothiazole, 4- methylbenzothiazole, S-methylbenzothiazole,S-bromobenzothiazole, 4-phenylbenzothiazole, S-phenylbenzothiazole,6-phenylbenzothiazole, 4-methoxybenzothiazole, 5- methoxybenzothiazole,5-iodobenzothiazole, 4-ethoxybenzothiazole, S-ethoxybenzothiazole,5-hydroxybenzothiazole, etc.); the naphthothiazole series (e.g.,tat-naphthothiazole, fi-naphthothiazole, S-methoxy-B-naphthothiazole,S-ethyI-fi-naphthothiazole, 8-methoxy-a-napthothiazole,7-methoxy-tat-naphthothiazole, etc.); those of the benzoxazole series(e.g., benzoxazole, S-chlorobenzoxazole, S-methylbenzoxazole,S-phenylbenzoxazole, S-methoxybenzoxazole, 5-ethoxybenzoxazole,S-hydroxybenzoxazole, etc.); those of the naphthoxazole series (e.g.,a-napthoxazole, fl-naphthoxazole, etc.); those of the benzoselenazoleseries (e.g., benzoselenazole, 5-chlorobenzoselenazole,S-methylbenzoselenazole, S-hydroxybenzoselenazole, etc.); those of thenaphtthoselenazole series (e.g., a-naphthoselenazole,,B-naphthoselenazole, etc.); those of the quinoline series including the2-quinolines (e.g., quinoline, 3-methylquinoline, S-methylquinoline,7-methylquinoline, S-methylquinoline, 6-chloroquinoline,8-chloroquinoline, 6-methoxyquinoline, 6-hydroxyquinoline,8-hydroxyquinoline, etc.); the 4-quinolines (e.g., quinoline,6-methoxyquinoline, 7-methoxyquinoline, 8-methoxyquinoline, etc.); thoseof the isoquinoline series (e.g., the l-isoquinoline, the3-isoquinolines, etc.); X and X each represents an atom selected fromthe group consisting of hydrogen, chlorine, bromine and iodine, at leastone of X and X being chlorine, bromine or iodine; R and R eachrepresents alkyl, e.g., lower alkyl such as methyl, ethyl, propyl,isopropyl, butyl, secondary butyl, tertiary butyl, etc., a sulfoalkylgroup in which the alkyl group has from 1 to 4 carbon atoms, such assulfomethyl, sulfoethyl, sulfopropyl, sulfobutyl, etc. and acarboxyalkyl group in which the alkyl group has from 1 to 4 carbon atomssuch as carboxymethyl, carboxyethyl, carboxypropyl, carboxybutyl, etc.;A represents an acid anion such as chloride, bromide, iodide,p-toluenesulfonate, thiocyanate, methyl sulfate, ethyl sulfate,perchlorate, and the like; and d, m, n and p each represents a positiveinteger of from Ito 2.

The halogen containing cyanine dyes described herein can be prepared byhalogenating a cyanine dye with chlorine, bromine or iodine. Anysuitable halogenating agent may be used, such as aqueous alcoholic(e.g., methanol or ethanol) solutions of the halogen,N-chlorosuccinimide, N-bromosuccinimide, N-iodosuccinirnide, or

a commercially available halogen-pyrrolidone complex,

such as the bromo-pyrrolidone complex sold by General Aniline and FilmCorp. Using such halogenating agents causes replacement by halogen or ahydrogen atom in the methine chain. In carbocyanines, ordicarbocyanines, analysis indicates that halogen substitution occurs onthe terminal carbon atoms of the methine chain. Typical preparations forthe halogen containing electron acceptors are as follows:

EXAMPLE A To 40 ml. of solution of ethyl alcohol containing 1() grams ofthe sensitizing dye, 1,1-diethyl-2,2- cyanine chloride is added 29 ml.of an aqueous solution containing 2X10' grams of a bromine-pyrrolidonecomplex sold by the General Aniline and Film Corp. The mixture of thesetwo solutions results in the conversion of the previously red coloredsolution of the dye (absorption max-540 m to a blue colored solution(absorption max590 m The blue form of the dye is light sensitive andshould be prepared and used only in total darkness to preventspontaneous decomposition.

A series of halogenated dyes are prepared by the drop- Wise addition ofa solution of 8 mg. N-bromosuccinimide (NBS) per ml. methanol to amethanolic solution of cyanine dye (8 mg. dye in cc. methanol), until nofurther color change occurs. At least one hydrogen atom in the methinechain of the dye is replaced with a bromine atom. The dyes used arelisted below, together with the number of equivalents NBS employed.

(A) l,1',3,3-tetramethyl-2,2-cyanine iodide, 2 NBS (B)3,3'-diethylthiacyanine iodide, 2 NBS (C) 3,3-diethylthiacarbocyanineiodide, excess NBS (D) 3,3-diethylthiadicarbocyanine iodide, excess NBS(E) 3,3-diethylthiatricarbocyanine iodide, excess NBS (F)3,3-diethyl-9-methylthiacarbocyanine bromide, ex-

cess NBS (G) 9-ethyl-3,3'-dimethyl-4,5,4',5-dibenzothiacarbocyaninechloride, excess NBS (H) 1,1'-diethyl-2,2'-cyanine chloride, 2 NBS (K)3,3'-dimethylthiacyanine bromide, 1 NBS (M)3-bromo-l,1'-diethyl-2,2-cyanine iodide, 3 NBS (N)l,l'-dimethyl-2,2-cyanine iodide, 3 NBS (O)l-ethyl-l'-methyl-2,2'-cyanine iodide, 3 NBS (P)l,3-dimethylthia-2'-cyanine iodide, 2 NBS (Q)1'-ethyl-2-methylthia-2'-cyanine iodide, 2 NBS (R)1'-methyl-3-ethylthia-2'-cyanine iodide, 2 NBS (S)l',3-diethylthia-2'-cyanine iodide, 2 NBS (T)3-ethyl-3-methylthiacyanine iodide, 2 NBS (U)1,1'-diethyl-l,2,2'-cyanine iodide, l NBS Another group of compoundswhich can be absorbed onto the fogged silver halide grains to improvereversal characteristics are halogen accepting compounds. Compounds ofthis type, organic or inorganic, can be characterized by having ananodic polarographic potential less than 0.85 and a cathodicpolarographic potential which is more negative than -1.0. A preferredclass of halogen accepting compounds is characterized by an anodichalfwave potential which is less than 0.62 and a cathodic halfwavepotential which is more negative than -1.3.

8 Particularl preferred halogen acceptors are merocyanine dyes havingthe following structure:

B=atoms required to complete a basic nitrogen-containing heterocyclicnucleus, e.g., benzothiazole, naphthothiazole, benzoxazole, etc.

-A=atoms required to complete an acidic heterocyclic nucleus, e.g.,rhodanine, 2-thiohydantoin, etc. Particularly good results are obtainedwith merocarbocyanine dyes (n=l) and with thiazole-rhodanine dyes.

Dyes of this class can be prepared by the methods described in Brookeret al. US. Pat. 2,493,747 and US. Pat. 2,493,748, issued Jan. 10, 1950.

Examples of suitable halogen accepting merocyanine dyes which can beused in the practice of this invention include:

Dye I--l -carboxymethyl-5-[ (3-ethyl-2-benzoxazolinylidene) ethylidene]-3-phenyl-2-thiohydantoin Dye II3-carboxymethyl-5-[(3-methyl-2-thiazolidinylidenel-methylethylidene] rhodanine DyeII-I3-ethyl-5- 3-methyl-Z-thiazolidinylidene ethylidene]-2-thio-2,4-oxazolidinedione Dye IV 53-{2-carboxyethyl}-2-thiazolidinylidene ethylidene] -3-ethylrhodanineDye V--5- (3-methyl-2-thiazolidinylidene) -1-methylethylidene] -3-2-rnorpholinoethyl) -rhodanine Dye VI5-(3-{2-carboxyethyl}-2-thiazolidinylidene) l-methylethylidene]-3-carboxyrnethylrhodanine Dye VII5-(3-{2-carboxyethyl}-2-thiazolidinylidene) l-methylethylidene] -3-2-methoxyethyl rhodanine Dye VIII-3- 3-dimethylaminopropyl -5-[(3-methyl- 2-thiazolidinylidene ethylidene] rhodanine Dye IX5-[(3-methyl-2-thiazolidinylidene) -1-methylethylidene] -3- (2-sulfoethyl)rhodanine The compounds which accept electrons or halogen in thepractice of this invention can be employed in widely varyingconcentrations. However, the electron accepting compounds are generallyemployed at concentrations in the range of about 200* to about 800,preferably about 300 to about 600 milligrams per mole of silver halide.The halogen accepting compounds are generally employed at somewhat lowerconcentrations.

The silver halides employed in the preparation of the electron sensitivecompositions described herein include any of the photographic silverhalides as exemplified by silver bromide, silver iodide, silverchloride, silver chlorobromide, silver bromoiodide, and the like. Silverhalide grains having an average grain size less than about one micron,preferably less than about 0.5 micron, give particularly good results.The silver halide grains can be any suitable shape such as cubic oroctahedral and preferably have a rather uniform diameter frequencydistribution. For example, at least by weight, of the photographicsilver halide grains can have a diameter which is within about 40%,preferably within about 30% of the mean grain diameter. Mean graindiameter, i.e., average grain size, can be determined using conventionalmethods, e.g., as shown in an article by Trivelli and Smith entitledEmpirical Relations Between Sensitometric and Size-FrequencyCharacteristics in Photographic Emulsion Series in The PhotographicJournal, vol. LXXIX, 1949, pages 330-338. A preferred class ofphotographic silver halides comprises at least 50 mole percent bromide,e.g., silver bromoiodide containing less than about ten mole percentiodide. The photographic silver halides can be coated at silvercoverages in the range of about 50 to about 500 milligrams of silver persquare foot of support.

Various colloids can be used as vehicles or binding agents for thesilver halide grains in the direct-positive materials of this invention.Satisfactory colloids which can be used for this purpose include any ofthe hydrophilic colloids generally employed in the photographic field,including, for example, gelatin, colloidal albumin, polysaccharides,cellulose derivatives, synthetic resins such as polyvinyl compounds,including polyvinyl alcohol derivatives, acrylamide polymers, and thelike. In addition to the hydrophilic colloids, the vehicle or bindingagent can contain dispersed polymerized vinyl compounds, particularlythose which increase the dimensional stability of photographicmaterials. Suitable compounds of this type include water-insolublepolymers of alkyl acrylates or methacrylates, acrylic acid, sulfoalkylacrylates or methacrylates, and the like. The silver halides can becoated without the use of a hydrophilic colloid, e.g., from an aqueoussolution or using vacuum deposition.

The electron sensitive compositions described herein can be coated on awide variety of supports in preparing the electrically conductingelements of this invention. The photographic silver halide grains can becoated on one or both sides of the support which is preferablysubstantially free of volatile solvent to prevent out gassing in avacuum and in preferably also transparent and/or flexible. Typicalcontinuous supporting sheets include, e.g., cellulose nitrate film,cellulose acetate film, polyvinyl acetal film, polystyrene film,polyethylene terephthalate film and other polyester film as well asglass, paper, metal, wood and the like. Supports such as paper which arecoated with a.-olefin polymers, particularly polymers of OL-OlCfiIlScontaining two or more carbon atoms, as exemplified by polyethylene,polypropylene, ethylenebutene copolymers, and the like, give goodresults.

The electron-sensitive recording elements of this inventionadvantageously carry a layer of electrically conductive material,preferably one having a surface resistivity of less than 10' ohms persquare. This material can be coated on the opposite side of the supportfrom the electron sensitive layer but it is generally coated on the sameside of the support that carries the sensitive layer. This conductivelayer serves to prevent accumulation of a static charge and consequentimage distortion where an electron beam strikes the sensitive element.This conductive layer can be the outermost layer on the emulsion side ofthe support. However, in some embodiments, it can be effectively locatedbeneath other coated layers on the support, i.e., beneath a fluorescentlayer, a sensitive layer, or both. If the conductive layer is beneathpermanent layers, then of course it must be able to withstand Whateverprocessing chemicals are to be used. If the layer is outermost it mustbe substantially electron transparent and it must be permeable bywhatever processing solutions are used. Preferably it is one that willnot be removed by processing chemicals and is optically transparent.This permanent conductive outer layer prevents static accumulations onthe surface during igmaewise exposure in an electron beam and again ifthe finished film is irradiated in an electron beam to view afluorescent image. The outer conductive layer may also be one that isremoved during processing, preferably by the same chemicals used forphotographic development, and in this case it need not be visuallytransparent though it must be substantially electron transparent. Apreferred conductive layer for use in the practice of this inventioncomprises a layer of film-forming vehicle or resin binder in which aredispersed colloidal particles of a semi-conducting metal compound suchas cuprous iodide or silver iodide, either as a colloidal dispersion oras a complexed solute. If desired, a conducting material can beimpregnated in the support to render the element an electricallyconducting element and eliminate the use of a separate electricallyconductive continuous layer.

The electrically conductive elements of this invention can containbarrier layers which are coated between a conducting layer or supportand the layer of electron sensitive material. Such barrier layers cansubstantially improve the stability of the electron sensitive layer. Ina preferred embodiment of this invention a continuous barrier layer iscoated outward from the supporting sheet and over a conductive layer andunder a layer of electron sensitive fogged silver halide grains. Such abarrier layer is moisture impermeable and preferably comprises a film ofwater-impermeable resin. A preferred class of resins for this purposecomprises homoand copolymers of vinylidene chloride including copolymerscontaining substantial amounts of vinylidene chloride with acrylicmonomers such as acrylonitrile, methyl acrylate, and the like. However,other suitable resins which can be used in the preparation of barrierlayers are electrically insulating resins generally having good waterimpermeability properties when coated as thin films. Examples of suchresins include polyvinyl butyryl, polymethyl methacrylate, polyvinylchloride, cellulose nitrate, polystyrene, polyesters such aspolyethylene terephthalate, polycarbonates and the like.

The direct electron recording films and plates described herein can alsocontain fluorescent layers or coatings to facilitate read-out. Suchcoatings or layers are located outward from the support and over thelayer of fogged silver halide grains. Examples of suitable organicfluorescent compounds which can be used in the fluorescent layers arethose described as organic fluors and organic scintillators in OrganicScintillation Detectors by E. Schram and R. Lombaert, ElsevierPublishing Company, 1963, as exemplified by such organic water-insolublefluorescent compounds as Tinopal SFG, p-terphenyl, pquaterphenyl,anthracene, 20% Fluolite casein, tetraphenyl butadiene, Blancopho-r AW,triazinyl-stilbenes such as those described in McFall et al. US. Patent2,933,390, bis(8 hydroxyquinolino)-magnesium, tris (4,4,4 trifluoro 1) 2(triethyl-l,3-butanediono)- europium,1,4-bis-2-(5-phenyloxazolyl)-benzene, Leucophor B (triazinyl aminostilbene) and coumarins such as those described in British Pat. No.786,234. These compounds are mentioned only as examples of the manyorganic, water-insoluble fluorescent compounds and mixtures thereofwhich can be used in practicing this invention. Layers of suchfluorescent compounds can be prepared using any procedure suitable forthis purpose. For example, the fluorescent compounds can be coated as adispersion in a hydrophilic film-forming binder such as gelatin,polyvinyl alcohol and other binders that can be coated from aqueoussolution to form Water permeable films. The fluorescent organiccompounds generally have a particle size up to about 5 microns. Apreferred class of binders which can be employed for the fluorescentcompound are vinyl polymers, e.g., alkyl acrylate styrene copolymers inwhich the alkyl groups preferably contain 1-8 carbon atoms, asexemplified by ethyl, methyl, butyl and the like, alkyl acrylateproteinand styrene-alkyl acrylate-protein emulsion polymerized latexes of thetype described in US. Pat. 2,852,382 as well as emulsion polymerizedresin binders of the type described in Fowler US. Pat. 2,772,166, issuedNov. 27, 1956, Dann et al. US. Pat. 2,831,767, issued Apr. 22, 1958 andGates et al. US. Pat. 2,853,457, issued Sept. 23, 1958. Mixtures of suchbinders can also be employed in forming the fluorescent layers describedherein.

The electron sensitive silver halide layers and other layers present inthe elements of this invention can be hardened with any suitablehardener, including aldehyde hardeners such as formaldehyde andmucochloric acid, aziridine hardeners, hardeners which are derivativesof dioxane, oxypoly-saccardies, such as oxy starch or oxy plant gums,and the like. The silver halide layers can also contain .additonaladditives, particularly those known to be beneficial in photographicemulsions, including, for example, lubricating materials, stabilizers,speed increasing materials, plasticizers, and the like. These layers canalso contain absorbing dyes which confine diffuse visible radia tionemitted by any fluorescent layer which is present during the exposure ofthe element of this invention to electrons. Although such dyes generallyreduce the sensitivity of photographic elements to light, they havesubstantially no effect upon the electron sensitivity of the elementsdescribed herein. Examples of suitable absorbing dyes include blueradiation absorbing dyes such as tartrazine and dyes of the typedescribed in Van Campen US. Pat. 2,956,879, issued Oct. 18, 1960. Thefogged silver halide layers described herein can also contain spectralsensitizing dyes which are advantageously employed where the silverhalide layer is exposed to ultraviolet, infrared or visible radiationand read-out in an electron beam. Suitable spectral sensitizers includethe cyanines, merocyanines, complex (trinuclear) cyanines, complex(trinuclear) merocyanines, styryls and hemicyanines. The silver halidelayers can also be developed using incorporated developers such aspolyhydroxybenzenes, aminophenols, B-pyrazolidones, and the like.

It is sometimes advantageous to employ surface active agents orcompatible mixtures of such agents in the preparation of theelectrically conductive materials described herein. Suitable agents ofthis type include non-ionic, ionic and amphoteric types, as exemplifiedby polyoxyalkylene derivatives, amphoteric amino acid dispersing agents,including sulfobetaines, and the like. Such surface active agents aredescribed in U.S. Pat. 2,600,831, issued June 17, 1952; U.S. Pat.2,271,622, issued Feb. 3, 1942; U.S. Pat. 2,271,623, issued Feb. 3,1942; U.S. Pat. 2,275,727, issued Mar. 10 1942; U.S. Pat. 2,787,604,issued Apr. 2, 1957; U.S. Pat. 2,816,920, issued Dec. 17, 1957; U.S.Pat. 2,739,891, issued Mar. 27, 1956 and Belgian Pat. 652,862.

This invention can be further illustrated by the following examples ofpreferred embodiments thereof although it will be understood that theseexamples are included merely for purposes of illustration and are notintended to limit the scope of the invention unless otherwisespecifically indicated.

EXAMPLE 1 The electron sensitive, direct-positive fogged silver halidegrains employed in the electron sensitive layers of the electricallyconductive elements of this invention can be the covered grain type. Toillustrate, a gelatin silver bromoiodide emulsion containing iridiumcenters in the core is prepared by simultaneously adding at 70 C., overa period of about 35 minutes in a controlled pAg of 8.9, (a) 1200milliliters of a 3.81 molar aqueous solution of potassium bromide and a0.1 molar, aqueous solution of potassium iodide and (b) 1275 millilitersof a 3.69 molar aqueous solution of silver nitrate, to 4000 millilitersof a 5% gelatin aqueous solution. Fifty milligrams of potassiumchloroiridate (III), i.e., K IrCl is added five minutes after the run isstarted. At the end of the run the emulsion is cooled to 40 C., gelatinis added to a total of 159 grams per mole of silver and the emulsion ischilled for about 15 hours, noodled and washed to remove soluble salts.The emulsion is then melted at 40 C. adjusted to a final Weight of 12.4kilograms a pH of 6.5 and a pAg of 8.2. Thiourea dioxide, in aqueoussolution, is added to the melted emulsion at a concentration of 0.002gram per mole of silver. The melt is then digested for one hour at 55 C.While holding at 55 C., 40 milligrams per mole of silver of patassiumchloroaurate is added to the melt from aqueous solution. The melt isthen digested for 20 minutes at 65 C. and then cooled to 40 C. Theemulsion is coated on a conventional cellulose acetate film sup portbearing a cuprous iodide conducting layer at a coverage of 100milligrams of silver per square foot in 384 milligrams of gelatin persquare foot.

Samples of the coated film are exposed to electron bombardment (50 kv.)in a conventional electron microscope (RCA Electron Microscope, ModelU2D) at a pressure of approximately 10- millimeters mercury for 0, 2, 4and 8 seconds. The exposed samples are processed for six minutes in anelonhydroquinone developer such as Kodak Developer D-19, fixed, washedand dried. The maximum density at each of the exposure levels is asfollows:

TABLE 1 Exposure (seconds): Density From the above table can be seenthan an increase in electron exposure significantly reduces density,i.e., there is obtained good reversal characteristics. Similar resultsare obtained when the potassium chloriridate in the above procedure isreplaced by other water soluble salts of metals of Group VIII of thePeriodic Table, for example, ammonium chloro palladate, potassium chloroplatinate, sodium chloro palladate and like salts which provide metalions which promote deposition of photolytic silver in the core of thefogged silver halide grains.

EXAMPLE 2 As previously indicated herein, electron acceptors can beabsorbed to the fogged silver halide grains in the sensitive layer. Toillustrate, a fine-grain, gelatino-silver bromoiodide emulsion is meltedat 40 C. Thiourea dioxide, in aqueous solution, is added to the meltedemulsion at a concentration of 0.002 g./mole silver. The melt is thendigested for one hour at 55 C. While holding at 55 C., 40 mg./molesilver of potassium chloroaurate is added to the melt from aqueoussolution, and the melt is then digested for 20 minutes at 65 C. The meltis cooled to 40 C. rapidly, and split into portions. From 2 00 to 800mg./mole silver of the electron acceptor, 1,1'-diethy1-2,2'- cyanineiodide reacted with an equal weight of N-bromosuccinimide (identified asDye U in Example B hereof), is added to various portions of the meltfrom methanol solution. Finally, the following addenda are added to eachmelt: 10 cc./mole Ag 10% aqueous formaldehyde, 25 cc./mole Ag saponinand 820 g./mole Ag 10% aqueous gelatin. These melts are coated on anelectrically conductive film support at coverages of 256 mg. Ag/ft. and338 mg. gelatin/K A sample of each coating is exposed 2, 4 and 8 secondsto electrons (50 kv.) in a conventional electron microscope at apressure of approximately 10- mm. Hg. The exposed samples are processed8 minutes in Kodak Developer D-19, fixed, washed and dried. The maximumand minimum densities for each sample are as follows:

TABLE 2 Dye (mg. /mole Coating Ag) Dmax} min 1 This value is the densityof the unexposed areas of each example. 2 This value is the densityresulting from an 8 second exposure.

Upon exposure and development after bleaching for 10 minutes at 68 F. inthe bleach composition described hereinbefore, each of the abovecoatings exhibits a loss of over 45% in maximum density.

EXAMPLE 3 TABLE 3 14 4 mil polyethylene terephthalate containing acuprous iodide conducting layer at coverages of 80 mg./ft. of silver and45 mg./ft. of gelatin. For comparison purposes a coating (Coating 2) isprepared from an identical portion of the aforementioned emulsion whichalso contains 400 mg. of dibrominated 1,1'-diethyl-2,2'-cyanine iodide(identified hereinbefore as Dye U). The coatings are given identicaltime scale exposures to electrons (15 kv.), developed for 6 minutes inKodak Developer D-19,

1O fixed, washed and dried. The results are as follows: Dye LightExposure Electron exposure TABLE 4 a D 1. ma. D in Coatmg (mg [mole Ag)Dm D x m Coating Relative speed Durex. D 1 200 3.0 0.67 3.0 3.0 2 400 a.0. 39 a. 0 a. 0 1 100 2. 0. 1s a 800 3.0 0.26 3.0 3.0 2 490 2.08 0.11change From the above table it can be seen that the addition E M L 4 ofan electron acceptor such as Dye U significantly in It is advantageousto include an absorbing dye in an electron sensitive layer of anelectrically conductive element used in the practice of this invention.To illustrate, a silver bromoiodide photographic emulsion containingapproximately 5 mole percent iodide and having an average grain size ofabout 0.08 micron is prepared by simultaneously adding, over a period of4.5 minutes at 55 C. (a) 1200 ml. of a 3.81 M KBr+0.1 M KI aqueoussolution and (b) 1275 ml. of a 3.69 M AgNO aqueous solution to 4000 ml.of a 5% gelatin aqueous solution containing 2.0 g. of K IrCl At the endof the additions, the emulsion is cooled, chill-set, noodled and washedto remove soluble salts. The emulsion is reduction and gold fogged byfirst adding 1.8 mg. of thiourea dioxide and heating for 60 minutes at65 C. and then adding 3.0 mg. of potassium chloroaurate per mole ofsilver halide and heating for 40 minutes at 65 C. Four hundred mg. ofanelectron acceptor (dibrominate 1,1- diethyl-2,2'-cyanine chlorideidentified as Dye U herein) per mole of silver halide are added. Ahardener and coating aid are added to the emulsion in the conventionalmanner, and the emulsion is coated on a 4 mil polyethylene terephthalatesupport coated with a conducting layer containing cuprous iodide. Theemulsion is coated at coverages of approximately 85 mg. of silver and 45mg. of gelatin/fe Over the emulsion layer is coated a fluorescent orscintillator layer at a coverage of 200 mg. of solids/ft. The binder forthe scintillator layer comprises 30% gelatin and 70% of a polymericlatex (70% butyl acrylate and 30% styrene copolymer). The polymericlatex contains a mixture of two scintillators (3 diphenyloxazole and0.3% 1,4-bis[2-(5 phenyl oxazolyl)]- benzene.

A similar coating is prepared except that the emulsion layer contains anabsorbing dye (tartrazine) at a concentration of 23 mg./it. Tartrazineis a yellow dye which absorbs blue light in the same region that thescintillator layer fluoresces.

A sample of each coating is exposed to electrons (15 kv.) in a vacuum at5 10- torr. The exposed coatings are processed for 6 minutes in aconventional elon-hydroquinone developer, fixed, washed and dried.

Upon inspection, it can be seen that the developed images in the coatingcontaining the absorbing dye is considerably more sharp in comparison tothe coating in which no absorbing dye is present in the emulsion layer.

EXAMPLE 5 The halogenated dyes described herein are particularlyeffective electron acceptors in the practice of this invention. Toillustrate, a gelatin silver bromoiodide (95:5 mole percent) is preparedusing the procedure of Example 1 except that the concentration of K IrClis increased to 0.425 g. per mole of Ag. The emulsion is coated(Coating 1) using the precedure of Example 1 on creases the electronsensitivity of the fogged silver halide grains. I

Similar results are obtained when Dye U is replaced by such electronacceptors as Dyes A, B, E, G, N, as identified hereinbefore.

EXAMPLE 6 Halogen accepting compounds can a so be absorbed onto thefogged silver halide grains employed in the electron sensitive layersdescribed herein. To illustrate, a gelatin silver chloride emulsion isprepared by simultaneously adding at 70 C., over a period of about 20minutes, 1000 ml. of a 4 molar silver nitrate aqueous solution and 1000ml. of a 4 molar sodium chloride aqueous solution, to a well-stirredaqueous solution of 1000 ml. of 0.01 molar sodium chloride containing 40grams of gelatin. Five thousand ml. of water containing 280 grams ofgelatin is added and the emulsion is cooled. One-eighth of the resultinggelatin silver chloride emulsion (containing 0.05 mole percent silverchloride) is melted at 40 C., mg. of potassium chloroiridite (dissolvedin water) is added and the emulsion heated to 70 C. This preparedemulsion constitutes the silver chloride core over which is formed ashell of silver chloride.

The shell of silver chloride is formed by adding to the core emulsion500 ml. of 4 molar silver nitrate aqueous solution and 500 ml. of 4molar silver chloride aqueous solution simultaneously over a period of20 minutes. One hundred sixty (160) grams of gelatin, previously soakedin 340 ml. of water, is stirred in and the emulsion cooled. During bothadditions of the silver nitrate and sodium chloride (i.e., to form boththe core and the shell), the two solutions are added at approximatelyconstant rates. Sufiicient silver chloride is formed in the shell togive a ratio of 4 moles of shell silver chloride to 1 mol of core silverchloride. The emulsion is washed in a conventional manner to removesoluble salts. The resulting covered grain emulsion is melted, thegelatin content increased to 160 grams per mole of silver chloride andwater added to 4000 grams per mole of silver chloride.

.025 milligrams of thiourea dioxide and 0.25 mg. of

potassium chloroaurate per mole are added to the emulsion at 40 C. Theemulsion is fogged by heating it to 65 C. and holding it for 20 minutesat this temperature. It is cooled immediately to 40 C. One hundred fiftymg./mole of Ag of 3-carboxymethyl-5-[(3-methyl- 2(3H)-thiazolinylidene)methylethylidene[rhodanine is incorporated into the emulsion. Theemulsion is coated with a conventional hardening agent and coating aidupon an electrically conducting polyethylene terephthalate support atcovereages of 360 mg. of Ag and 270 mg. of gelatin/ft? The coating isexposed to electron bombardment (15 kv.,), developed for 2 minutes inKodak Developer D-19, fixed, washed and dried. The coating shows goodreversal clfiaragteristics and exhibits a D of 2.48 and a D o 0.1

Similar results are obtained when the halogen acceptor employed in theabove procedure is replaced with other halogen acceptors such as Dyes I,III, VI and IX, as identified hereinbefore or when silver chlorobromidegrains, particularly those having a 50:50 molar ratio of halide are usedin place of the silver chloride grains.

Thus by the practice of this invention there is provided electricallyconductive direct-positive silver halide elements suitable for use indirect electron recording. Such elements can be used in data recording,television recording, electron microscopes and the like. They can beexposed to electrons using any voltages generally suitable for thispurpose although in most applications they are exposed at voltages inthe range of about to about 50 kv., and most often in the range of aboutto about 40 kv.

We claim:

1. An electrically conductive element comprising a support and a layercomprising electron-sensitive, directpositive, fogged silver halidegrains (A) wherein said fogged silver halide grains contain internalcenters which promote the deposition of photolytic silver and have acovering comprising a fogged 'silver halide that develops to silverwithout exposure or (B) wherein said fogged silver halide grains (1) aresuch that a test portion thereof, when coated as a photographic silverhalide emulsion on a support to give a maximum density of at least about1 upon processing for 6 minutes at about 68 F. in Kodak DK-SO developer,has a maximum density which is at least about 30% greater than themaximum density of an identical coated test portion which is processedfor 6 minutes at about 68 F. in Kodak DK-SO developer after beingbleached for about 10 minutes at about 68 F. in a bleach composition of:

Potassium cyanide-50 mg. Acetic acid .(glacial)-3.47 cc. Sodiumacetate-41.49 g. Potassium bromide-119 mg. Water to1 liter and (2) haveabsorbed thereon about 200 to about 800 mg. per mole of silver of anelectron-accepting cyanine dye having at least one methine group whereinthe hydrogen atom is replaced with a halogen atom having an atomicweight in the range of about 35 to about 127.

2. The electrically conductive element of claim 1 in which said foggedsilver halide grains comprise a central core of silver halide containingcenters which promote deposition of photolytic silver and an outer shellcovering said core comprising a fogged silver halide that develops tosilver without exposure.

3. The electrically conductive element of claim 1 in which (1) saidfogged silver halide grains are such that a test portion thereof, whencoated as a photographic silver halide emulsion on a support to give amaximum density of at least about 1 upon processing for 6 minutes atabout 68 F. in Kodak DK-50 developer, has a maximum density which is atleast about 30% greater than the maximum density of an identical coatedtest portion which is processed for 6 minutes at about 68 F. in KodakDK-SO developer after being bleached for about 10 minutes at about '68"F. in a bleach composition of:

Potassium cyanide-50 mg.

Acetic acid (glacial)3.47 cc.

Sodium acetate11.49 g.

Potassium bromidel19 mg.

Water to1 liter and (2) adsorbed on saidfo-gged silver halide grains isabout 200 to about 800 mg. per mole of silver of an electron acceptingcyanine dye having at least one methine group wherein the hydrogen atomthereof is replaced with a halogen atom having an atomic weight in therange of about 35 to about 127.

4. The electrically conductive element of claim 3 in which said electronaccepting cyanine dye has the following general formula:

9 OX \CH GH/N \GH ext/ c (L L)u 1 35 R2 A wherein Z and Z eachrepresents the non-metallic atoms necessary to complete a heterocyclicnucleus containin from 5 to 6 atoms and including a hetero atom selectedfrom the group consisting of oxygen, sulfur, nitrogen and selenium; Lrepresents a methine group; X and X each represents an atom selectedfrom the group consisting of hydrogen, chlorine, bromine and iodineatoms, at least one of X and X being selected from the group consistingof chlorine, bromine and iodine; R and R each represents an alkylsubstituent; A represents an anion; and d, m, n and 11 each represents apositive integer of from 1 to 2.

5. The electrically conductive element of claim 2 in which said silverhalide grains are fogged with a combination of a reduction fogging agentwith a gold fogging agent.

6. The electrically conductive element of claim 3 in which said silverhalide grains are fogged with a combination of a reduction fogging agentwith a gold fogging agent.

7. The electrically conductive element of claim 2 in which said foggedsilver halide grains comprise a central core of silver halide containingcenters attributable to Group VIII metal ions which centers promotedeposition of photolytic silver and an outer shell covering said corecomprising a fogged silver halide that develops to silver withoutexposure.

8. The electrically conductive element of claim 7 in which there isadsorbed on said fogged silver halide grains about 200 to about 800 mg.per mole of silver, of an electron accepting cyanine dye having at leastone methine group wherein the hydrogen atom thereof is replaced with ahalogen atom having an atomic weight in the range of about 35 to about127.

9. The electrically conductive element of claim 7 in wnich said GroupVIII metal ions are iridium ions.

10. The electrically conductive element of claim 5 in which saidreduction fogging agent is thiourea dioxide, said gold fogging agent ispotassium chloroaurate and said fogged silver halide grains have anaverage grain size less than about 1 micron.

11. The electrically conductive element of claim 6 in which saidreduction fogging agent is thiourea dioxide, said gold fogging agent ispotassium chloroaurate and said fogged silver halide grains have anaverage grain size less than about 1 micron.

12. The electrically conductive element of claim 2 in which said foggedsilver halide grains have an average grain size less than about 1 micronand comprise at least 50 mole percent 'bromide.

13. The electrically conductive element of claim 3 in which said foggedsilver halide grains have an average grain size less than about 1 micronand comprise at least 50 mole percent bromide.

14. The electrically conductive element of claim 8 in which there isadsorbed on said fogged silver halide grains about 200 to about 800 mg.per mole of silver of 1,1-diethyl-2,2-cyanine chloride wherein each ofthe hydrogen atoms of the methine chain thereof is replaced with abromine atom.

15. The electrically conductive element of claim 13 in which there isadsorbed on said fogged silver halide grains about 200 to about 800 mg.per mole of silver of 1,1'-di- 17 ethyl-2,2'-cyanine chlorine whereineach of the hydrogen atoms of the methine chain thereof is replaced witha Ibromine atom.

16. The electrically conductive element of claim 1 in which said supportcomprises a continuous supporting sheet, an electrically conductivecontinuous layer on said supporting sheet and a water-impermeablecontinuous barrier layer outward from said supporting sheet over saidconductive layer and under said layer comprising fogged silver halidegrains.

17. The electrically conductive element of claim 16 in which saidelectrically conductive layer comprises dispersed cuprous iodide in afilm-forming vehicle and said water-impermeable barrier layer comprisesa film of water-impermeable resin.

18. The electrically conductive element of claim 16 in which saidcontinuous supporting sheet is a linear polyester sheet.

19. The electrically conductive element of claim 1 which comprises afluorescent layer outward from said supporting sheet over said layer offogged silver halide grains, said fluorescent layer comprising anorganic water-insoluble fluorescent compound dispersed in a film ofhydrophilic film-forming binder.

20. The electrically conductive element of claim 19 in which saidhydrophilic film-forming binder is a copolymer of an alkyl acrylate withstyrene.

21. The electrically conductive element of claim 19 in which said layerof fogged silver halide garins comprises an absorbing dye.

22. The process which comprises exposing to electrons, an electricallyconductive element comprising a support and a layer comprising electronsensitive direct-positive fogged silver halide grains.

23. The process according to claim 22 wherein said electricallyconductive element is exposed to electrons in a vacuum.

24. The process according to claim 22 wherein said electricallyconductive element is exposed at a pressure of about 10 millimeters ofmercury.

25. A method of forming an image record which can be developed to adiscernible positive image comprising exposing to electrons anelectrically conductive element comprising a support and a layercomprising electronsensitive-direct-positive, fogged silver halidegrains.

26. A process according to claim 25 wherein said fogged silver halidegrains will record an image record when exposed to electrons in avacuum.

27. A process according to claim 25 wherein said fogged silver halidegrains will record an image record when exposed to electrons at anatmospheric pressure of about 10- millimeters of mercury.

28. A process according to claim 25 wherein said fogged silver halidegrains comprise a central core of silver halide containing centers whichpromote deposition of photolytic silver and an outer shell covering saidcore comprising a fogged silver halide that develops to silver withoutexposure.

29. A process according to claim 25 wherein said fogged silver halidegrains are such that:

(l) a test portion thereof, when coated as a photographic silver halideemulsion on a support to give a maximum density of at least about 1 uponprocessing for 6 minutes at about 68 F. in Kodak DK-SO developer, has amaximum density which is at least about 30% greater than the maximumdensity of an identical coated test portion which is processed for 6minutes at about 68 F. in Kodak DK-SO developer after being bleached forabout 10 minutes at about 68 F. in a bleach composition:

Potassium cyanidemg. Acetic acid (glacial)3.47 cc. Sodium acetate11.49g. Potassium bromidel19 mg. Water to-1 liter and (2) adsorbed on saidfogged silver halide grains is about 200 to about 800 mg. per mole ofsilver of an electron-accepting cyanine dye having at least one methinegroup wherein the hydrogen atom thereof is replaced with a halogen atomhaving an atomic weight in the range of about 35 to about 127.

30. A process according to claim 25 wherein said electrically conductiveelement comprises at least one layer containing .an electricallyconductive material having a surface resistivity of less than 10 ohmsper square.

31. A method according to claim 25 wherein said silver halide grainshave an average size of less than about 1 micron.

References Cited UNITED STATES PATENTS 3,184,313 5/1965 Rees et al 250 X3,237,008 2/1966 Dostes et al. 25065 3,303,341 2/1967 Fram et al. 250653,353,185 11/1967 Nitka 25049.5 X 2,996,382 8/ 1961 Luckey et al. 96683,206,313 9/1965 Porter et al. 96l08 3,367,778 2/ 1968 Berriman 9664FOREIGN PATENTS 1,027,146 4/ 1966 Great Britain.

WILLIAM L. JARVIS, Primary Examiner US. Cl. X.R.

727 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,51 O, 3MB Dated ay 5, 1 97 Invencor(s) Dugald A. Brooks, Evan T. Jonesand Richard W. Spayd It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

I'" Column 1 line 35, after "beam" should be inserted "I Column 2, line22, "eectron" should read --electron--. Column 5, line 73, "a" shouldread --the--. Column 6, after line 30,

the formula reading line 56, "naphtthoselenazole" should read--naphthoselenazole-. Column 7, line 16, after "halogen", "or" shouldread --of--; line 25, the dye formula commencing with "1 ,1-" shouldread 1 ,1 line 26, "29 ml." should read --20 ml.--; line 614., thatportion of dye (U) set forth as "-1 ,2,2' should read -2,2 Column 9,line 58, "igmaewise" should read -imagewise--; line 37, that portion offormula reading "-1 )-2 (triethyl-" should read -1-)-2- (thienyl)-Column 1 0, line 70, "oxypolysaccardies" should read--oxy"polysaccharides--. Column 11 line 65, "patassium" should read--potassium--. Column 13, line 36, "dibrominate" should read--dibrominated--. Column 114., line 53, "mol" should read --mole--; line65, that portion of formula reading "-methylethylidenef" should read-methylethyliden line 69, "covereages" should read --coverages--. Column15, line #8, "absorbed" should read --adsorbed-- Page 1 of 2 pages i -WUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,5 ,3L Dated y 5, 97

Inventor(s) Dugald A.Brooks,Evan T.Jones and Richard W.Spayd It iscertified that error appears in the above-identified patent and tn'ltsaid Letters Patent are hereby corrected as shown below:

Eolumn '16, after columnar line 9, that portion of the formula '1reading Column 17, line 29, "gar-ins" should read -grains--. Column 18,line 16, after "composition" should be inserted --of--.

SIGNED ANI. QEALED BEAL) AM Edward H. Fletcher, Ir. A g Officer III-LIA!I. W, 38. M11 Comissioner of Patents L .1

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